schedule reboot { at time | delay interval }

When can you use this command?

You can always use it 🙂

Seriously telling, you can use it in cases, when there is probability that your work and a new configuration can cause a device to be unavailable. Sometimes it is necessary to change a configuration of a device, which is not accessible by console, but only by remote connection. Specially if you are changing IP addresses or doing some experiments with access methods of the device. Even if you tested everything in your lab and you are sure that everything will go smoothly, it is better to remember about this function. People make mistakes. After you configured schedule reboot function, you are sure that all your mistakes can be repair by reboot of the device, with the restriction that the new configuration is not saved. Of course I am talking about some small or less important devices. For more important or crucial devices it is recommended to use console connection (console server).

Remember to turn this function off when you are sure that everything works properly!

Routing protocols are used to discover routes to a destination. Only one routing protocol at one time determines the optimal route to a destination.

What happens if we have different routes to the same destination learnt by different routing protocols?

When multiple routing information sources coexist on the same router, the router with the highest preference is selected as the optimal route.

Below you can find the default route preferences by each routing protocol (the smaller the value, the higher the preference is):

Of course you can change these default values manually.

But what happens if different routing protocols are configured with the same preference?

Huawei routers define external and internal preferences. Default external preferences are showed in the above table and can be set manually by users, whereas internal preferences are fixed and cannot be changed. For example, two routes, static and OSPF, which have the same route preference 5, set by command, can reach the destination 2.2.2.2/32. According to the internal preferences listed below, route discovered by OSPF will be selected as an optimal route:

#
interface Ethernet0/0/0
undo shutdown
ip address 10.0.0.1 255.255.255.252
#
interface LoopBack0
ip address 1.1.1.1 255.255.255.255
#
ip route-static 2.2.2.2 255.255.255.255 10.0.0.2 preference 5
#
ospf 1
preference 5
area 0.0.0.0
network 1.1.1.1 0.0.0.0
network 10.0.0.0 0.0.0.3
[labnario]display ip routing-table
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 6 Routes : 6
Destination/Mask Proto Pre Cost Flags NextHop Interface
1.1.1.1/32 Direct 0 0 D 127.0.0.1 LoopBack0
2.2.2.2/32 OSPF 5 1 D 10.0.0.2 Ethernet0/0/0
10.0.0.0/30 Direct 0 0 D 10.0.0.1 Ethernet0/0/0
10.0.0.1/32 Direct 0 0 D 127.0.0.1 Ethernet0/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0

Huawei, to meet your expectations, recently announced the launch of an enterprise network simulation platform eNSP for ICT practitioners. This information you can find at official Huawei website.

To be honest, I have not tested it yet. If I find time I will do it this week. I have already installed this simulator on my notebook and it looks promising. We can build a network based on AR1200 routers and enterprise switches.

The only think you have to do is to register at Huawei website, download and install the simulator.

I forgot to mention that this simulator is completely for free.

To make it easy for you, below you can find a direct link to the Huawei eNSP:

eNSP

Please feedback your comments if you test it. I would like to know your opinion.

Enjoy!

Sometimes we can meet such situation on a router or a switch:

 [labnario]display users
  User-Intf    Delay    Type   Network Address     AuthenStatus    AuthorcmdFlag
+ 34  VTY 0   00:00:00  TEL    172.29.12.226             pass           no      Username : huawei
  35  VTY 1   00:08:01  TEL    172.29.12.226             pass           no      Username : labnario
  36  VTY 2   00:07:38  TEL    172.29.12.226             pass           no      Username : killer
  37  VTY 3   00:07:00  TEL    172.29.12.226             pass           no      Username : killer
  38  VTY 4   00:01:34  TEL    172.29.12.226             pass           no      Username : labnario

By default, on Huawei device, there are 5 vty lines available. If all these lines are occupied by users, no other user is able to access the device. Such situation can appear in 2 cases:

1. The device is fully occupied by telnet users.
2. All telnet sessions are hang.

The first case is normal and it can often happen. Sessions will be deleted when users log out from the device or their sessions’ idle-timeout expires. By default idle-timeout is set to 10 minutes.

The second case can be caused by idle-timeout of vty lines set to 0:

#
user-interface vty 0 4
 authentication-mode aaa
 idle-timeout 0 0
#

It means that this session never expires. If a user forget to log out from a device, vty line is still being occupied. This causes that a next user has no possibility to telnet the device.

If you have access by console port or you are already logged in by telnet, you can delete all unnecessary telnet sessions:

<labnario>free user-interface vty 4
Warning: User interface VTY4 will be freed. Continue? [Y/N]:y
 [OK]
<labnario>display users
  User-Intf    Delay    Type   Network Address     AuthenStatus    AuthorcmdFlag
+ 34  VTY 0   00:00:00  TEL    172.29.12.226             pass           no      Username : huawei
  35  VTY 1   00:13:14  TEL    172.29.12.226             pass           no      Username : labnario
  36  VTY 2   00:12:51  TEL    172.29.12.226             pass           no      Username : killer
  37  VTY 3   00:12:13  TEL    172.29.12.226             pass           no      Username : killer

To avoid such situation, configure idle-timout for vty lines different than 0:

#
user-interface vty 0 4
 authentication-mode aaa
 idle-timeout 15 0
#

You can also set maximum-vty sessions to 15 and configure the same parameters for all vty lines:

[labnario]user-interface maximum-vty 15 
[labnario]user-interface vty 0 14
 authentication-mode aaa
 idle-timeout 15 0

Now you have 16 vty lines available.

Maybe it should have been shown at the beginning of this blog…

As you probably know, Huawei datacom devices are divided in 2 segments: Telco and Enterprise. But what you decide to choose depends on you. You do decide which device you want to use, regardless of it is intended for telco or enterprise. You know the best which device is appropriate for your network. Having detailed technical specification you are able to choose the device which meets your requirements.

For those who don’t know where to find information about Huawei’s portfolio, I am sending direct links to proper pages:

Huawei Telco